grab samples

ALTERNATIVE METHOD FOR SEAWATER - SPECIFIC ION ELECTRODE (Warner 1971 )
References
With seawater samples, follow exactly the same analysis procedure as for sediment samples.
AMERI CA N PUBLIC HEALTH ASSOCIATION. AMERICAN WATER WORKS ASSOCIATION. AND WATER POLLUTION CONTROL FEDERATION.
1975. Siandard methods ror the examina tio n orwater and waSlewater. 14th ed. Washington. D.C. 1193 p.
ENVIRONMENTAL PROTECTION AGENCY. 1974. Methods o rchemical analysis or water and wastes EPA 625/6-74-003a: 298 p.
GREENHALGH. R., AND J. P. RILEY. 1961. The determination or nuorides in natural waters. with particular rderence to sea water. Anal.
Chim. Acta 25: 179-188.
MCQUAKER, N. R .. AND M. JOURNEY . 1977. Delermination or IOlal fluoride in soil and vegetation using alkali ru sion-specific-ion
electrode technique. Anal. Chem. 49: 53 - 56.
WARNER. T. 1971 . Normal fluoride content orseawater. Deep Sea Res. 18: 1255-1263.
6.16 Petroleum-based Hydrocarbons
Theestimation of petroleum hydrocarbons in marine samples is complicated by such problems as: (I)
the complexity of petroleum hydrocarbon mixtures; (2) crude petroleum composition varies depending on
the source; (3) hydrocarbon mixtures are also formed naturally (biogenic hydrocarbons); (4) natural
seepages and other geological processes introduce petroleum to the oceans; and (5) various diagenetic
processes occur in the sediments which can alter the characteristics and fractions of the com ponents of the
hydrocarbon mixtures (both biogenic and petroleum). As Farrington and Tripp ( 1975) have noted" ...
there has yet to be a report of a complete analysis of a single crude oil, and it is unlikely there will be in the
near future. "
The method suggested below was chosen as one of the simplest and most straight forward techniques
presently available for separating petroleum-based hydrocarbons from other hydrocarbons which may be
present in the environment. Analysts should keep abreast of the literature in this field, however, for future
im provemen ts.
II. Summary
In the described technique, the hydrocarbons are extracted from the sediment by hexane. The
fluorescence of the unknown in hexane is compared to standards of chrysene. The use of chrysene as a
standard material is discussed by Cretney and Wong (1974).
III. Sample Preparation (based on Levy 197 I; Hargrave and Phillips 1975)
(I) Only high quality reagents should be used . All glassware, reagents and filter paper should be
carefully checked for fluorescence. It may be necessary to redistill reagents in all-glass systems to lower the
blank values; however, items with persistently high" blank" fluorescence values should not be used.
(2) Drain wet sediment on hexane rinsed (Whatman no. I) filter paper over vacuum, and then divide
into two portions. On one portion, determine the moisture content, and on the other portion, determine the
hexane soluble substances as outlined below.
(3) Place 0.2-2 g of damp sediment in a 50-ml Pyrex centrifuge tube (thoroughly cleaned with
hexane); add I ml distilled water and 10 ml of hexane. The ratio of distilled water to hexane is critical
(Hargrave and PhiJlips 1975). The sample size is also dependent on the particle size of the sediments and
the suspected hydrocarbon content (use more sample when particles are large).
(4) Shake thoroughly for 5 min. Allow to settle, drain off the hexane extract through a filter paper
(presoaked in hexane) containing about 5 g of anhydrous sodium sulphate (previously rinsed with
hexane), and collect in a 25-ml volumetric flask. Repeat the hexane-water extraction procedure. Wash the
sodium sulphate on the filter paper with not more than 5 ml of hexane, combine the wash with the extracts
and make up to 25 ml with hexane.
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